Is It Better to Adopt 2 Puppies or Just 1?

Adopting a pair at the same time is not the best idea. The puppies may seek comfort from each other, not you — which may lead to behavioral problems.

Siblings can bond so strongly that they can't bond with humans or other dogs easily. By:
Siblings can bond so strongly that they can’t bond with humans or other dogs easily. Photo: hernan.mojarro

Most people aren’t zealous or brave enough to adopt 2 pups at the same time.

But imagine you’re holding 2 balls of puppy love in your arms, slobbered with big laps of puppy breath. The shelter worker or breeder nudges you that 2 pups are better than 1. You go home with a matched set.

Adopting 2 pups at the same time is generally not a good idea, according to many animal behaviorists. A lot of rescue groups and breeders are now in agreement. The behavioral problems and challenges that can go along with raising super-bonded siblings now has a name: littermate syndrome.

Over the years, I can recall at least 4 pairs of dogs brought in as 8-week-old puppies and raised as 1 inseparable canine entity. These siblings were the closest you could get to a canine version of Siamese twins, conjoined in every way except an actual physical attachment. The dogs experienced behavioral problems growing up and were not easy to raise or train.

Maybe I’m super sensitive to the problems encountered when “twins” go home instead of just 1 pup, being the proud mom of identical twin boys. Human boys, that is. But I can attest to the fact that “twin worlds” exist, and raising intensely bonded babies has unique challenges. So does raising twin pups.

What Is Littermate Syndrome?

If 2 puppies become hyper-bonded, they can become so emotionally dependent upon each another that they have difficulty relating to humans or other dogs.

Learning basic coping mechanisms and picking up on important human–canine communication signals is difficult or impossible for them. This bond and the personality traits and training challenges associated, is littermate syndrome.

Training 1 puppy is challenging, but you have the advantage of a one-on-one relationship with your puppy. With 2 pups, their deep bond to each other may impede their ability to develop a strong human bond to you or to other humans or canines. They are so tuned in to each other that it’s hard to teach them needed social skills.

The hallmark behavioral problem of littermate syndrome is fearfulness of people and often other dogs, which leads to training hurdles. These puppies seek comfort from each other, not you.

Because aggression is so often fear-based, these pups may become aggressive or “spooky.” Or they may simply seem to remain distant, detached.

Spend time separately with each dog to help socialize them. By:
Spend time separately with each dog to help socialize them. Photo: twid


If your trip to the shelter results in taking Harold and Maude home instead of just Harold, don’t assume littermate syndrome is a foregone conclusion. Early intervention is the key to well-socialized pups.

Let’s take a look at nature vs. nurture.


Breed characteristics, genetics and personality traits affect the likelihood of littermate syndrome developing.

I remember a pair of Golden Retriever puppies. They never displayed fear or aggression, traits that are not common in the breed, but they also never doted on humans, a trait that is common to the breed.

During physicals, all they wanted to do was get off the table and run to their sibling. Most Goldens love the exam table, love the exam, love everyone! These dogs never focused on or took treats from me or their people.

I also remember a pair of young mixed-breed pups, Border Collie wannabes. They were already hyper-bonded, having been caged together in a shelter. They were intelligent and shy. Their young family kept them together 24/7 after adoption. Fearfulness and distrust of the outside world grew worse with age. They almost looked feral as they gripped and huddled in the corner of any room they were in.


Our natural instinct is to want our pets to bond, to play together, to enjoy each other’s company.

In order to avoid littermate syndrome, however, separating your 2 puppies facilitates socialization. They need to bond with you, not just their sibling. This seems counterintuitive.

  1. Train them separately. This means individual sessions, walks, etc. It’s double the work — which is bordering on driving you crazy.
  2. Crate them separately. This fosters self-confidence.
  3. Make separate puppy play dates and individual trips to the vet. Again, this is more than twice the work and commitment.
  4. Have an older dog in the house.
  5. Acquire 2 pups at different times. Let them develop their own personalities and then introduce them to your menagerie.

This video by Dr. Katrina Warren explains the pros and cons of raising littermates:

YouTube player

Double Trouble

In my waiting room, bystanders love to make comments to people who are having trouble controlling 2 dogs at once. This brings back memories of people making comments to me, a young mother of twins. If I heard “double trouble” once, I heard it a thousand times.

The peanut gallery on the South Philly corner loved seeing my Suburban-size twin stroller roll down the block. “Double trouble, I see, sweetheart.” Older wise guys took this opportunity to comment on my fecundity. Classmates at vet school loved to say that I had had a litter instead of a baby. No wonder I hate the phrase “double trouble.”

My twins are now grown and enjoying great lives on opposite sides of the country. We all survived our struggles to avoid human littermate syndrome, if you will.

As for socialization in the outside world, a big obstacle my young twins faced was making close relationships away from the family “crate.”

How do you make a best friend when you already have one? Other kids are intimidated by the intense bond twins share. Same goes in the canine world. Not only do bonded pups often have a harder time relating to other dogs, but the other dog can be intimidated by trying to befriend “the pack.”

As people become more aware of this syndrome as a risk — again, not a foregone conclusion — early steps to avoid it can help tremendously.

Apologies to my 31-year-old sons, if comparing you to puppies was out of line. I’m hoping you’re too busy to read this, enjoying life and your own happy shelter pups you’ve raised so beautifully. Our pups can learn a lot from us. And we can learn so much from them.



This pet health content was written by a veterinarian.